detached f6aceff

fix(vt): preserve reflow boundaries across regions

commit
f6aceffdd6755b61ec5c82fe9d4b476d9f98fb5e
author
brice · · 2026-07-15 15:42 UTC
parent
8040975
signature
GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email
4 files · +119 -6
Unified
UnifiedSplit
M pkg/vt/buffer.go +16 -6
@@ -67,17 +67,27 @@ func (b *buffer) clear(y, x0, x1 int) {
6767 }
6868
6969 func (b *buffer) scrollUp(top, bottom, n int) {
70- for ; n > 0; n-- {
71- copy(b.boundaries[top:bottom], b.boundaries[top+1:bottom+1])
72- b.boundaries[bottom] = lineBoundary{}
70+ // A region operation changes which rows meet at both region edges. A soft
71+ // boundary belongs to the row it follows, not the cells moved into its
72+ // neighbor, so sever links crossing either edge before reflow can observe
73+ // them.
74+ b.hard(top - 1)
75+ copy(b.boundaries[top:bottom-n+1], b.boundaries[top+n:bottom+1])
76+ for y := bottom - n + 1; y <= bottom; y++ {
77+ b.boundaries[y] = lineBoundary{}
7378 }
79+ b.hard(bottom - n)
7480 }
7581
7682 func (b *buffer) scrollDown(top, bottom, n int) {
77- for ; n > 0; n-- {
78- copy(b.boundaries[top+1:bottom+1], b.boundaries[top:bottom])
79- b.boundaries[top] = lineBoundary{}
83+ // See scrollUp: the old top no longer follows the row above the region, and
84+ // the last moved row no longer precedes the row below it.
85+ b.hard(top - 1)
86+ copy(b.boundaries[top+n:bottom+1], b.boundaries[top:bottom-n+1])
87+ for y := top; y < top+n; y++ {
88+ b.boundaries[y] = lineBoundary{}
8089 }
90+ b.hard(bottom)
8191 }
8292
8393 func (b *buffer) hydrate() {
@@ -67,17 +67,27 @@ func (b *buffer) clear(y, x0, x1 int) {
67 }67 }
68 68
69 func (b *buffer) scrollUp(top, bottom, n int) {69 func (b *buffer) scrollUp(top, bottom, n int) {
70- for ; n > 0; n-- {70+ // A region operation changes which rows meet at both region edges. A soft
71- copy(b.boundaries[top:bottom], b.boundaries[top+1:bottom+1])71+ // boundary belongs to the row it follows, not the cells moved into its
72- b.boundaries[bottom] = lineBoundary{}72+ // neighbor, so sever links crossing either edge before reflow can observe
73+ // them.
74+ b.hard(top - 1)
75+ copy(b.boundaries[top:bottom-n+1], b.boundaries[top+n:bottom+1])
76+ for y := bottom - n + 1; y <= bottom; y++ {
77+ b.boundaries[y] = lineBoundary{}
73 }78 }
79+ b.hard(bottom - n)
74 }80 }
75 81
76 func (b *buffer) scrollDown(top, bottom, n int) {82 func (b *buffer) scrollDown(top, bottom, n int) {
77- for ; n > 0; n-- {83+ // See scrollUp: the old top no longer follows the row above the region, and
78- copy(b.boundaries[top+1:bottom+1], b.boundaries[top:bottom])84+ // the last moved row no longer precedes the row below it.
79- b.boundaries[top] = lineBoundary{}85+ b.hard(top - 1)
86+ copy(b.boundaries[top+n:bottom+1], b.boundaries[top:bottom-n+1])
87+ for y := top; y < top+n; y++ {
88+ b.boundaries[y] = lineBoundary{}
80 }89 }
90+ b.hard(bottom)
81 }91 }
82 92
83 func (b *buffer) hydrate() {93 func (b *buffer) hydrate() {
A pkg/vt/region_reflow_test.go +52 -0
@@ -0,0 +1,52 @@
1+package vt
2+
3+import (
4+ "testing"
5+
6+ "github.com/stretchr/testify/require"
7+)
8+
9+func TestResizeSeversSoftWrapsAtRegionalScrollEdges(t *testing.T) {
10+ tests := []struct {
11+ name string
12+ seq string
13+ want []string
14+ }{
15+ {
16+ name: "CSI S",
17+ seq: "\x1b[2;4r\x1b[S",
18+ want: []string{"ABC", "IJK", "LMN", "OP ", " ", "QRS"},
19+ },
20+ {
21+ name: "CSI T",
22+ seq: "\x1b[2;4r\x1b[T",
23+ want: []string{"ABC", " ", "EFG", "HIJ", "KL ", "QRS"},
24+ },
25+ {
26+ name: "insert lines",
27+ seq: "\x1b[2;4r\x1b[2;1H\x1b[L",
28+ want: []string{"ABC", " ", "EFG", "HIJ", "KL ", "QRS"},
29+ },
30+ {
31+ name: "delete lines",
32+ seq: "\x1b[2;4r\x1b[2;1H\x1b[M",
33+ want: []string{"ABC", "IJK", "LMN", "OP ", " ", "QRS"},
34+ },
35+ }
36+
37+ for _, tt := range tests {
38+ t.Run(tt.name, func(t *testing.T) {
39+ s := NewScreen(4, 5)
40+ s.Write([]byte("ABCDEFGHIJKLMNOPQRST"))
41+ s.Write([]byte(tt.seq))
42+
43+ s.Resize(3, 6)
44+
45+ got := make([]string, s.Frame.Height)
46+ for y := range s.Frame.Height {
47+ got[y] = rowString(s.Frame.Row(y))
48+ }
49+ require.Equal(t, tt.want, got)
50+ })
51+ }
52+}
@@ -0,0 +1,52 @@
1+package vt
2+
3+import (
4+ "testing"
5+
6+ "github.com/stretchr/testify/require"
7+)
8+
9+func TestResizeSeversSoftWrapsAtRegionalScrollEdges(t *testing.T) {
10+ tests := []struct {
11+ name string
12+ seq string
13+ want []string
14+ }{
15+ {
16+ name: "CSI S",
17+ seq: "\x1b[2;4r\x1b[S",
18+ want: []string{"ABC", "IJK", "LMN", "OP ", " ", "QRS"},
19+ },
20+ {
21+ name: "CSI T",
22+ seq: "\x1b[2;4r\x1b[T",
23+ want: []string{"ABC", " ", "EFG", "HIJ", "KL ", "QRS"},
24+ },
25+ {
26+ name: "insert lines",
27+ seq: "\x1b[2;4r\x1b[2;1H\x1b[L",
28+ want: []string{"ABC", " ", "EFG", "HIJ", "KL ", "QRS"},
29+ },
30+ {
31+ name: "delete lines",
32+ seq: "\x1b[2;4r\x1b[2;1H\x1b[M",
33+ want: []string{"ABC", "IJK", "LMN", "OP ", " ", "QRS"},
34+ },
35+ }
36+
37+ for _, tt := range tests {
38+ t.Run(tt.name, func(t *testing.T) {
39+ s := NewScreen(4, 5)
40+ s.Write([]byte("ABCDEFGHIJKLMNOPQRST"))
41+ s.Write([]byte(tt.seq))
42+
43+ s.Resize(3, 6)
44+
45+ got := make([]string, s.Frame.Height)
46+ for y := range s.Frame.Height {
47+ got[y] = rowString(s.Frame.Row(y))
48+ }
49+ require.Equal(t, tt.want, got)
50+ })
51+ }
52+}
M pkg/vt/snapshot.go +8 -0
@@ -199,6 +199,14 @@ func PreflightVisibleBlob(data []byte) (DecodeStats, error) {
199199 return DecodeStats{}, fmt.Errorf("preflight visible: %w", errInvalidHistory)
200200 }
201201 }
202+ if string(data[:4]) == visibleMagicV2 {
203+ for range height {
204+ if uint64(binary.BigEndian.Uint32(p.data[:4])) > width || p.data[4] > 1 {
205+ return DecodeStats{}, fmt.Errorf("preflight visible: %w", errInvalidHistory)
206+ }
207+ p.data = p.data[5:]
208+ }
209+ }
202210 return DecodeStats{Rows: height, Cells: cells, Styles: cells, Bytes: bytes}, nil
203211 }
204212
@@ -199,6 +199,14 @@ func PreflightVisibleBlob(data []byte) (DecodeStats, error) {
199 return DecodeStats{}, fmt.Errorf("preflight visible: %w", errInvalidHistory)199 return DecodeStats{}, fmt.Errorf("preflight visible: %w", errInvalidHistory)
200 }200 }
201 }201 }
202+ if string(data[:4]) == visibleMagicV2 {
203+ for range height {
204+ if uint64(binary.BigEndian.Uint32(p.data[:4])) > width || p.data[4] > 1 {
205+ return DecodeStats{}, fmt.Errorf("preflight visible: %w", errInvalidHistory)
206+ }
207+ p.data = p.data[5:]
208+ }
209+ }
202 return DecodeStats{Rows: height, Cells: cells, Styles: cells, Bytes: bytes}, nil210 return DecodeStats{Rows: height, Cells: cells, Styles: cells, Bytes: bytes}, nil
203 }211 }
204 212
A pkg/vt/snapshot_boundary_test.go +43 -0
@@ -0,0 +1,43 @@
1+package vt
2+
3+import (
4+ "encoding/binary"
5+ "testing"
6+
7+ "github.com/stretchr/testify/require"
8+)
9+
10+func TestPreflightVisibleV2RejectsMalformedBoundaries(t *testing.T) {
11+ s := NewScreen(4, 2)
12+ s.Write([]byte("abcdef"))
13+ blob, err := s.MarshalPrimaryVisible()
14+ require.NoError(t, err)
15+
16+ boundaryOffset := 13 + 2*4*historyCellBytes
17+ tests := []struct {
18+ name string
19+ mutate func([]byte)
20+ }{
21+ {
22+ name: "boundary end exceeds row width",
23+ mutate: func(data []byte) {
24+ binary.BigEndian.PutUint32(data[boundaryOffset:boundaryOffset+4], 5)
25+ },
26+ },
27+ {
28+ name: "soft flag is not canonical",
29+ mutate: func(data []byte) {
30+ data[boundaryOffset+4] = 2
31+ },
32+ },
33+ }
34+
35+ for _, tt := range tests {
36+ t.Run(tt.name, func(t *testing.T) {
37+ data := append([]byte(nil), blob...)
38+ tt.mutate(data)
39+ _, err := PreflightVisibleBlob(data)
40+ require.Error(t, err)
41+ })
42+ }
43+}
@@ -0,0 +1,43 @@
1+package vt
2+
3+import (
4+ "encoding/binary"
5+ "testing"
6+
7+ "github.com/stretchr/testify/require"
8+)
9+
10+func TestPreflightVisibleV2RejectsMalformedBoundaries(t *testing.T) {
11+ s := NewScreen(4, 2)
12+ s.Write([]byte("abcdef"))
13+ blob, err := s.MarshalPrimaryVisible()
14+ require.NoError(t, err)
15+
16+ boundaryOffset := 13 + 2*4*historyCellBytes
17+ tests := []struct {
18+ name string
19+ mutate func([]byte)
20+ }{
21+ {
22+ name: "boundary end exceeds row width",
23+ mutate: func(data []byte) {
24+ binary.BigEndian.PutUint32(data[boundaryOffset:boundaryOffset+4], 5)
25+ },
26+ },
27+ {
28+ name: "soft flag is not canonical",
29+ mutate: func(data []byte) {
30+ data[boundaryOffset+4] = 2
31+ },
32+ },
33+ }
34+
35+ for _, tt := range tests {
36+ t.Run(tt.name, func(t *testing.T) {
37+ data := append([]byte(nil), blob...)
38+ tt.mutate(data)
39+ _, err := PreflightVisibleBlob(data)
40+ require.Error(t, err)
41+ })
42+ }
43+}

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